The present dry development method constitutes an improvement of the dry development method disclosed and claimed in copending U.S. patent application, Ser. No. 752,040 filed Dec. 20, 1976, now abandoned. In the latter connection, dry development processing as contemplated herein and in the aforesaid U.S. application requires a photoresist material which may have a differential etchant rate of reactivity related to its selectively exposed areas and non-exposed areas, when subjected to an oxygen-containing gas in which monatomic oxygen and/or ozone are present as a reactive oxygen species wherein the differential rate of reactivity to an etchant treatment involving the reactive oxygen species is sufficiently large to enable the portion of the layer of photoresist material subject to the greater etchant rate to be completely removed from the underlying substrate surface before any substantial part of the remaining portion of the photoresist material is so removed. A desired pattern as determined by a latent image imparted to the layer of photoresist material through its selective exposure to a suitable energy source, such as ultraviolet radiation, X-ray, or E-beam radiation, is thereby developed in the layer of photoresist material by dry processing as contrasted to the conventional practice of employing liquid chemical solvents as selective etchants.